Sling for Engineer — Onboarding

When NOT to use Sling

Easier to learn from than "when to use." These are the failure-mode patterns we keep seeing.

You're still figuring out the architecture. Use Claude Code interactively. Sling is for after the architect decides.
The brief is <3 lines. If it's that small, just write it. The 3 minutes you save aren't worth the round-trip.
It touches prod auth, payments, or HIPAA paths. Tier 3 — Sling will refuse anyway, save the round-trip.
Cross-cutting refactor across 10+ files. Use Claude Code with multi-file edits. Sling self-iterates per file (3 attempts each) which gets expensive past ~8 files.
You need it shipped in 5 min. Production hotfixes — open the editor.

Six phases. Each writes a row to task_steps. You can replay individual phases on retry.

On retry, completed phases are skipped (checkpointed in Postgres). Workspace + branch are reused.

Mode	Trigger	Best for
`stiv` (default)	No special label	Well-scoped, single-file, TDD-friendly
`claude-code`	Label `claude-code`	Multi-file, exploratory — recommended today
`claude-code-tmux`	Label `claude-code-tmux`	Same as above + live `tmux attach` for debugging

Mode resolution: task label → repo config (execution_mode) → task property → default (stiv).

config/repositories.json — per-repo: `branch`, `testCmd`, `execution_mode`, `hipaa_mode`, `blockedPaths`
Issue label skip-tests — bypass Phase 1 (test generation)
Issue label force-rereview — one-shot bypass of the SHA-dedup gate on PR auto-review
Env WORKER_MODEL / OPENROUTER_TRIAGE_MODEL — model overrides; never bypass resolveModel()
Env SLING_TICKET_BUDGET_USD — per-ticket cost cap (default $25)

Categories from failure-classifier.js. Each is reported on the PR + dashboard.

Generated tests pass but existing suite fails. Most often: brittle existing test referencing an old field name.

tsc errors. Usually a missing type import on a refactor.

Easy — re-run usually fixes. If repeated, the lint config drifted.

Per-ticket cost cap hit. Brief is too big — split it or raise the cap on this one ticket.

Hit the worker timeout. Long compile / test suite — bump CLAUDE_CODE_TIMEOUT_MS for the run.

Risk assessment refused. Touches auth/payments/PHI. Implement by hand.